Identification of a fault in a finite state machine

Abstract

A computer-implemented method and a processing module for identifying that a fault has occurred in a finite-state machine (FSM). It is determined whether a set of one or more transitions that have occurred between states of the FSM is allowable. In response to determining that the set of one or more transitions is not allowable, it is identified that a fault has occurred in the FSM.

What is claimed is: 
     
         1 . A computer-implemented method of identifying that a fault has occurred in a finite-state machine (FSM), the method comprising:
 determining whether a set of one or more transitions that have occurred between states of the FSM is allowable; and   in response to determining that the set of one or more transitions is not allowable, identifying that a fault has occurred in the FSM.   
     
     
         2 . The method of  claim 1 , wherein said determining is performed in dependence on a data record comprising at least one predefined set of one or more transitions. 
     
     
         3 . The method of  claim 2 , wherein said determining comprises:
 comparing the set of one or more transitions that have occurred between states of the FSM with the data record comprising the at least one predefined set of one or more transitions; and   determining that the set of one or more transitions is not allowable in response to said comparison.   
     
     
         4 . The method of  claim 2 , wherein a first group comprises predefined allowable sets of one or more transitions between states of the FSM, and a second group comprises predefined unallowable sets of one or more transitions between states of the FSM, and the data record comprises the sets of the group comprising the fewest predefined sets out of the first and second groups. 
     
     
         5 . The method of  claim 2 , wherein the number of transitions in the set of one or more transitions that have occurred is equal to the number of transitions in one of the at least one predefined set of one or more transitions in the data record. 
     
     
         6 . The method of  claim 1 , further comprising recording the set of one or more transitions that have occurred between states of the FSM in a transition history. 
     
     
         7 . The method of  claim 6 , wherein said determining is performed in dependence on the transition history. 
     
     
         8 . The method of  claim 6 , wherein the transition history is configured to record up to a maximum number of transitions. 
     
     
         9 . The method of  claim 8 , wherein the number of transitions in the set of one or more transitions that have occurred does not exceed the maximum number. 
     
     
         10 . The method of  claim 8 , wherein said determining is performed in dependence on a data record comprising at least one predefined set of one or more transitions and the maximum number of transitions is determined based on the at least one predefined set of one or more transitions in the data record. 
     
     
         11 . The method of  claim 2 , wherein said determining is performed in response to detecting that the number of transitions that have occurred is equal to the number of transitions in one of the at least one predefined set of one or more transitions in the data record. 
     
     
         12 . The method of  claim 1 , wherein the method is performed while the FSM is active and responding to input data. 
     
     
         13 . The method of  claim 1 , further comprising, in response to identifying that a fault has occurred in the FSM:
 replaying the FSM from a first state corresponding to a first transition in the set of one or more transitions that have occurred; and   in response to determining that the same set of one or more transitions has occurred between states of the FSM, determining that the fault that has occurred is a stuck-at-fault.   
     
     
         14 . A processing module configured to identify that a fault has occurred in a finite-state machine (FSM), the processing module comprising:
 a verification unit configured to determine whether a set of one or more transitions that have occurred between states of the FSM is allowable; and   a fault signalling unit configured to identify that a fault has occurred in the FSM if the verification unit indicates that the set of one or more transitions is not allowable.   
     
     
         15 . The processing module of  claim 14 , wherein the verification unit is configured to perform said determining in dependence on a data record comprising at least one predefined set of one or more transitions. 
     
     
         16 . The processing module of  claim 15 , wherein the verification unit is configured to perform said determining by:
 comparing the set of one or more transitions that have occurred between states of the FSM with the data record comprising the at least one predefined set of one or more transitions; and   determining that the set of one or more transitions is not allowable in response to said comparison.   
     
     
         17 . The processing module of  claim 15 , wherein the verification unit is configured to perform said determining in response to detecting that the number of transitions that have occurred is equal to the number of transitions in one of the at least one predefined set of one or more transitions in the data record. 
     
     
         18 . The processing module of  claim 14 , further comprising a memory configured to record the set of one or more transitions that have occurred between states in the FSM in a transition history. 
     
     
         19 . The processing module of  claim 18 , wherein the verification unit is configured to perform said determining in dependence on the transition history stored in the memory. 
     
     
         20 . A non-transitory machine readable storage medium having stored thereon an integrated circuit definition dataset that, when processed in an integrated circuit manufacturing system, configures the integrated circuit manufacturing system to manufacture a processing module configured to identify that a fault has occurred in a finite-state machine (FSM), the processing module including:
 a verification unit configured to determine whether a set of one or more transitions that have occurred between states of the FSM is allowable; and   a fault signalling unit configured to identify that a fault has occurred in the FSM if the verification unit indicates that the set of one or more transitions is not allowable.